Method of manufacturing a heat transfer system for aircraft structures

ABSTRACT

A method of manufacturing a heat transfer system is provided that includes, in one form, preparing a heat conducting array by perforating at least a portion of the heat conducting array, wrapping the heat conducting array around foam elements, placing a heat conducting spreader along one surface area of the foam elements, placing a lower skin over the heat conducting spreader, placing an upper skin over an opposite surface area of the foam elements to create a structural assembly, and curing the structural assembly. A material of the foam elements flows through the perforated portion of the heat conducting array during the curing step.

FIELD

The present disclosure relates to avionics or equipment bays foraircraft, and in particular, method of manufacturing systems formanaging heat to improve cooling of electronics within the bays.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Most aircraft, or air vehicles, typically include a number of bays thathouse a variety of equipment, such as avionics, batteries, diagnosticequipment, and servicing ports, among others. These bays extend into theinterior of the aircraft to define a cavity, and are covered byremovable doors or access panels so that the aircraft can maintain asmooth outer moldline surface for aerodynamic performance.

During operation, certain components located within these equipment bayscan reach high temperatures, which can cause premature failure, and thusa means to provide cooling to these components is often provided.Typical methods may include integrated fans or cooling ducts, inaddition to vents or louvers that allow airflow to enter the equipmentbays during flight. Some equipment bays, however, are required to besealed from moisture intrusion during operations, which limits certaincooling options, such as the vents or louvers. Accordingly, sealedequipment bays that include heat generating components, such aselectronic components on printed circuit boards, or batteries, present achallenge in providing the requisite cooling to prevent prematureequipment failure.

SUMMARY

In one form of the present disclosure, a method of manufacturing a heattransfer system is provided that comprises preparing a heat conductingarray by perforating at least a portion of the heat conducting array,wrapping the heat conducting array around foam elements, placing a heatconducting spreader along one surface area of the foam elements, placinga lower skin over the heat conducting spreader, placing an upper skinover an opposite surface area of the foam elements to create astructural assembly, and curing the structural assembly. A material ofthe foam elements flows through the perforated portion of the heatconducting array during the curing step.

In another form, a method of manufacturing a heat transfer system isprovided that comprises preparing a heat conducting array by perforatingat least a portion of the heat conducting array, the heat conductingarray comprising a pyrolytic graphite sheet (PGS) material, wrapping theheat conducting array around foam elements, placing a heat conductingspreader along one surface area of the foam elements, the heatconducting spreader comprising a pyrolytic graphite sheet (PGS)material, placing a lower skin over the heat conducting spreader,placing an upper skin over an opposite surface area of the foam elementsto create a structural assembly, and curing the structural assembly. Amaterial of the foam elements flows through the perforated portion ofthe heat conducting array during the curing step.

In still another form, a method of manufacturing a heat transfer systemis provided that comprises preparing a heat conducting array byperforating at least a portion of the heat conducting array, wrappingthe heat conducting array around core elements, placing a lower skinover one surface area of the core elements, placing an upper skin overan opposite surface area of the core elements to create a structuralassembly, and forming the structural assembly. A material of the coreelements extends through the perforated portion of the heat conductingarray during the forming step.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

In order that the disclosure may be well understood, there will now bedescribed various forms thereof, given by way of example, referencebeing made to the accompanying drawings, in which:

FIG. 1 is a perspective view of an exemplary air vehicle illustratingvarious equipment bays in which the principles of the present disclosureare applied;

FIG. 2 is a top perspective view of one form of a system for managingheat transfer constructed in accordance with the principles of thepresent disclosure;

FIG. 3 is a bottom perspective view of the system for managing heattransfer in accordance with the principles of the present disclosure;

FIG. 4 is another bottom perspective view, with certain componentsremoved for purposes of clarity, of the system for managing heattransfer in accordance with the principles of the present disclosure;

FIG. 5 is an offset cross-sectional view, taken along line 5-5 of FIG.3, illustrating various components of the system for managing heattransfer in accordance with the principles of the present disclosure;

FIG. 6 is the offset cross-sectional view of FIG. 5 illustrating heatflow through the various components, including the heat conductingmembers, according to the principles of the present disclosure;

FIG. 7 is a perspective view of a plurality of heat conducting membersconstructed in accordance with the principles of the present disclosure;

FIG. 8 is an end view of a heat conducting member constructed inaccordance with the principles of the present disclosure;

FIG. 9 is a perspective view of an alternate form of the heat conductingmembers constructed in accordance with the principles of the presentdisclosure;

FIG. 10 is an end view of a structural member and heat conducting arrayconstructed in accordance with the principles of the present disclosure;

FIG. 11 is an end view of another form of a heat conducting arrayconstructed in accordance with the principles of the present disclosure;

FIG. 12 is a perspective view of a heat conducting array that extendsthrough the structural member and constructed in accordance with theprinciples of the present disclosure; and

FIG. 13 is a flow diagram illustrating a manufacturing process inaccordance with the principles of the present disclosure.

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses.

Referring to FIG. 1, an air vehicle is illustrated and generallyindicated by reference numeral 10. The air vehicle 10 includes a numberof equipment bays 12 that house a variety of equipment such as avionicsor batteries, and in this particular illustration, a plurality ofavionics boards 14 having electronic components that generate heatduring operation. Additionally, some or all of the equipment bays 12 maybe sealed in order to prevent moisture intrusion during operation, whichis described in greater detail below.

The equipment bays 12 are covered by access panels, or hatches, whichare not shown for purposes of clarity. The access panels cover thecavities 16 defined by the equipment bays 12 and generally conform tothe outer moldline shape of the air vehicle 10, which in thisillustrative example are upper wing moldlines. It should be understoodthat the air vehicle 10 and its configuration of equipment bays 12 ismerely exemplary, and thus any number and/or size of equipment bays 12may be employed in a variety of different types of air vehicles whileremaining within the scope of the present disclosure.

Referring now to FIGS. 2 through 5, an exemplary avionics board 14 isillustrated and has at least one heat-generating component 20 disposedthereon, such as a radio frequency power amplifier. In one form, theavionics board 14 and heat-generating component(s) 20 are part of asystem 22 for managing heat transfer according to the principles of thepresent disclosure that is better illustrated in FIG. 5. As shown, thesystem 22 includes the avionics board 14 and heat-generating components20 within the cavity 16, which defines an inner wall portion 24. Aplurality of heat conducting members 30 are disposed adjacent oneanother as shown (and also in FIGS. 3 and 4), which are positionedbetween the heat generating components 20 and the inner wall portion 24of the cavity 16. The plurality of heat conducting members 30 generallycomprise a core 32 and an outer shell 34 wrapped around at least aportion of the core 32. The outer shell 34 comprises a material having arelatively high thermal conductivity, and in one form is at least onesheet of pyrolytic graphite sheet (PGS) material. The cores 32 arethermally conductive, and in one form are a thermally conductive foam.Furthermore, the cores 32 are resilient in one form of the presentdisclosure, such that the heat conducting members 30 are more capable ofwithstanding impact loads. As used herein, the term “resilient” shouldbe construed to mean having properties that allow the cores 32 toelastically or plastically deform under load. Additional details of theheat conducting members 30 and variants thereof are set forth in greaterdetail below.

As further shown in FIG. 5, the system 22 also comprises at least onethermally conductive element 40 disposed between the heat conductingmembers 30 and the heat generating components 20. In one form, thethermally conductive elements 40 are thermal gap filler pads that have athermal conductivity of about 5 W/mK. The system 22 also includes apressure-sensitive adhesive (PSA) layer 42 in contact with the innerwall portion 24 to secure the heat conducting members 30 to the cavity16. (The PSA layer 42 is also shown in FIG. 3). Alternately, a layer ofstiffening material 44 may be disposed over the heat conducting members30 and next to the PSA layer 42 in order to provide additional stiffnessto the plurality of heat conducting members 30. In one form, thisstiffening material 44 is a copper material, however, it should beunderstood that other materials that exhibit both thermal conductivityand an appropriate stiffness may also be employed while remaining withinthe scope of the present disclosure.

The system 22 also includes a structural member 50 disposed proximatethe inner wall portion 24 of the cavity 16, which in this form comprisesan upper skin 52, a lower skin 54, and a foam core 56 disposed betweenthe upper skin 52 and the lower skin 54. As shown, at least one heatconducting array 60 extends through the foam core 56 and between theupper skin 52 and the lower skin 54. The heat conducting array 60 isalso, in one form, a pyrolytic graphite sheet (PGS) material. The heatconducting array 60, in this form, includes at least one upper cap 62,at least one lower cap 64, and a wall portion 66 extending between theupper cap 62 and the lower cap 64. The caps 62 and 64 may also beunderstood as flanges or legs that extend away from or between the wallportions 66 as illustrated herein. As shown, the upper caps 62 aredisposed proximate a heat source, which in this illustration is theheat-generating components 20 and the elements therebetween. Furtherdetails of the heat conducting array 60, and variants thereof, are setforth in greater detail below.

As further shown, an optional heat conducting spreader 68 is disposedbetween the lower caps 64 of the heat conducting array 60 and the lowerskin 54 of the structural member 50, in one form of the presentdisclosure. Similar to forms of the heat conducting member 30 and theheat conducting array 60, the heat conducting spreader 68 is also apyrolytic graphite sheet (PGS) material in one form of the presentdisclosure.

In an alternate form, a moisture-proof layer 69 is disposed over theupper skin 52 in an application where the cavity 16 is to be sealed frommoisture intrusion. In this form, the moisture-proof layer 69 is anethylene-co-methacrylic acid (EMAA) material, although it should beunderstood that other moisture-proof materials may be employed whileremaining within the scope of the present disclosure.

Referring now to FIG. 6, the system 22 and its heat transfercharacteristics are illustrated and described in greater detail. Asindicated by the arrows, in operation, heat that is generated from thecomponents 20 is transferred to the heat conducting members 30 and thethermally conductive elements 40. The heat is then transferred throughthe PSA layer 42 (and also the stiffening material 44 if present), tothe upper skin 52 of the structural member 50. From there, the heattransfers through the upper caps 62 of the heat conducting array 60,then down through the wall portions 66, to the lower caps 64, to theheat conducting spreader 68, and then out to the atmosphere through thelower skin 54. Accordingly, the system 22 provides efficient andeffective heat transfer paths in order to dissipate the heat generatedby components 20. In preliminary testing, the temperature differencebetween the heat generating components 20 and the lower skin 54 wasreduced by about fourteen percent (14%). In other words, about fourteenpercent (14%) of the heat generated by the components 20 did not reachthe lower skin 54.

Further details of the heat conducting members 30 are now described withreference to FIGS. 7 and 8. As previously set forth, the heat conductingmembers 30 include a core 32 and an outer shell 34 wrapped around atleast a portion of the core 32. The outer shells 34 of the heatconducting members 30 are in physical contact with each other as shownin FIG. 7 in order to provide improved heat transfer characteristics. Inthis form, the heat conducting members 30 have a generally rectangularconfiguration as illustrated. It should be understood that othergeometric configurations for the heat conducting members 30, one ofwhich is set forth in greater detail below, are to be construed asfalling within the scope of the present disclosure.

As shown more clearly in FIG. 8, the outer shells 34 of the heatconducting members 30 are wrapped completely around the cores 32. In oneform, the outer shells 34 extend around the cores 32 to define anoverlap region 70. Accordingly, one end of the outer shell 34 extendsover, or overlaps, the other end of the outer shell 34 in order tocompletely encase the core 32. It should be understood that the outershells 34 can be configured to be wrapped completely around the cores 32in other joint configurations, such as a butt or step-lap joint, whileremaining within the scope of the present disclosure. Additionally, insome configurations, it is contemplated that the outer shells 34 may bediscontinuous or not wrap completely around the cores 32 while remainingwithin the scope of the present disclosure.

Referring now to FIG. 9, another configuration of the heat conductingmembers is illustrated and generally indicated by reference numeral 30′.In this configuration, the heat conducting members 30′ define a gridconfiguration of individual elements 80, that in one form are inphysical contact with one another and that have outer shells 34′ thatcompletely encase the cores 32′. It should be understood, however, thatother grid configurations having varying geometries for the individualelements 80, and different outer shell configurations as set forthabove, shall be construed as falling within the scope of the presentdisclosure.

Referring now to FIG. 10, the structural member 50 and heat conductingarray 60 are described in greater detail. As previously set forth, theheat conducting array 60 extends through the foam core 56 and betweenthe upper skin 52 and the lower skin 54 of the structural member. Theheat conducting array 60 in one form is a continuous piece, however, itshould be understood that the heat conducting array 60 may bediscontinuous and/or formed from separate pieces while remaining withinthe scope of the present disclosure.

The upper skin 52 and lower skin 54 in one form are a Kevlar® material,although it should be understood that other types of fiber-reinforcedcomposites such as carbon-fiber composites or glass-fiber composites mayalso be employed, in addition to various types of metallic structures.In one form, the foam core 56 comprises a low density, high strengthpolystyrene foam material, such as Spyderfoam. Additionally, thestructural member 50 in this form is an aircraft skin, however, itshould be understood that this application is merely exemplary and thatother forms of structure such as internal spars or ribs, or structuresof other vehicles, buildings, or other devices may be employed whileremaining within the scope of the present disclosure.

As shown, the wall portions 66 of the heat conducting array 60 extendvertically between the upper caps 62 and the lower caps 64 in one formof the present disclosure. It should be understood, however, that thewall portions 66′ may extend at an angle as shown in FIG. 11, creatingwhat is commonly referred to as a “hat” configuration for the heatconducting array 60′. Other variations, including but not limited to“J,” “L,” or “T” configurations may also be employed according to theheat conducting and structural load requirements of a particularapplication. Accordingly, it should be understood that a variety offorms of heat conducting arrays 60 may be employed while remainingwithin the scope of the present disclosure.

Advantageously, as shown in FIG. 12, the wall portions 66 define aplurality of apertures 90, which create openings that allow material ofthe foam core 56 to migrate through during manufacturing. Theseapertures 90 provide for improved structural integrity by enhancing thebond between the wall portions 66 and the foam core 56. The manufactureof the structural member 50, and more specifically the heat conductingarray 60 and apertures 90, is now described in greater detail.

Referring to FIG. 13, the heat conducting array 60 is prepared byperforating at least a portion of the heat conducting array 60, such asthe wall portions 66. The heat conducting array 60 is then wrappedaround the core elements 32, and the heat conducting spreader 68 isplaced along one surface area of the core elements 32. The lower skin 54is placed over the heat conducting spreader 68, and the upper skin 52 isplaced over an opposite surface area of the core elements 32 to create astructural assembly. The structural assembly is then cured, eitherthrough a room temperature and standard atmospheric pressure cure or avacuum autoclave cure, by way of example, wherein a material of the coreelements 32 flows through the perforated portions 90 of the heatconducting array 60 during the curing step. As set forth above, thisresults in an interface between the heat conducting array 60 and thecore elements 32 with improved structural integrity.

It should be understood that the order of these manufacturing steps aremerely exemplary and that other orders of the steps may be employed,such as placing the upper skin 52 over the heat conducting spreader 68and the core elements 32 before the lower skin 54, while remainingwithin the scope of the present disclosure. Additionally, it should beunderstood that the heat conducting spreader 68 is optional and thus thestructural assembly can be formed without this member while remainingwithin the scope of the present disclosure. Furthermore, the structuralassembly may be formed in a press, either heated or non-heated, whileremaining within the scope of the present disclosure.

It should be noted that the disclosure is not limited to the variousforms described and illustrated as examples. A large variety ofmodifications have been described and more are part of the knowledge ofthe person skilled in the art. These and further modifications as wellas any replacement by technical equivalents may be added to thedescription and figures, without leaving the scope of the protection ofthe disclosure and of the present patent.

1. A method of manufacturing a heat transfer system comprising:preparing a heat conducting array by perforating at least a portion ofthe heat conducting array; wrapping the heat conducting array aroundfoam elements; placing a heat conducting spreader along one surface areaof the foam elements; placing a lower skin over the heat conductingspreader; placing an upper skin over an opposite surface area of thefoam elements to create a structural assembly; and curing the structuralassembly, wherein a material of the foam elements flows through theperforated portion of the heat conducting array during the curing step.2. The method according to claim 1, wherein the structural assembly iscured by at least one of a room temperature and standard atmosphericpressure cure, and a vacuum autoclave cure.
 3. The method according toclaim 1, wherein the heat conducting array is a pyrolytic graphite sheet(PGS) material.
 4. The method according to claim 1, wherein the heatconducting spreader is a pyrolytic graphite sheet (PGS) material.
 5. Themethod according to claim 1, wherein the heat conducting array definesat least one upper cap, at least one lower cap, and a wall portionextending between the upper cap and the lower cap when wrapped aroundthe foam elements, and the wall portion is perforated.
 6. The methodaccording to claim 1 further comprising applying a moisture-proof layerover the upper skin.
 7. The method according to claim 6, wherein themoisture-proof layer is an ethylene-co-methacrylic acid (EMAA) material.8. A method of manufacturing a heat transfer system comprising:preparing a heat conducting array by perforating at least a portion ofthe heat conducting array, the heat conducting array comprising apyrolytic graphite sheet (PGS) material; wrapping the heat conductingarray around foam elements; placing a heat conducting spreader along onesurface area of the foam elements, the heat conducting spreadercomprising a pyrolytic graphite sheet (PGS) material; placing a lowerskin over the heat conducting spreader; placing an upper skin over anopposite surface area of the foam elements to create a structuralassembly; and curing the structural assembly, wherein a material of thefoam elements flows through the perforated portion of the heatconducting array during the curing step.
 9. The method according toclaim 8, wherein the structural assembly is cured by at least one of aroom temperature and standard atmospheric pressure cure, and a vacuumautoclave cure.
 10. The method according to claim 8, wherein the heatconducting array defines at least one upper cap, at least one lower cap,and a wall portion extending between the upper cap and the lower capwhen wrapped around the foam elements, and the wall portion isperforated.
 11. The method according to claim 8 further comprisingapplying a moisture-proof layer over the upper skin.
 12. The methodaccording to claim 11, wherein the moisture-proof layer is anethylene-co-methacrylic acid (EMAA) material.
 13. A method ofmanufacturing a heat transfer system comprising: preparing a heatconducting array by perforating at least a portion of the heatconducting array; wrapping the heat conducting array around coreelements; placing a lower skin over one surface area of the coreelements; placing an upper skin over an opposite surface area of thecore elements to create a structural assembly; and forming thestructural assembly, wherein a material of the core elements extendsthrough the perforated portion of the heat conducting array during theforming step.
 14. The method according to claim 13, wherein the heatconducting array is a pyrolytic graphite sheet (PGS) material.
 15. Themethod according to claim 13 further comprising placing a heatconducting spreader between the lower skin and the core elements. 16.The method according to claim 15, wherein the heat conducting spreaderis a pyrolytic graphite sheet (PGS) material.
 17. The method accordingto claim 13, wherein the core elements are foam.
 18. The methodaccording to claim 13, wherein the heat conducting array defines atleast one upper cap, at least one lower cap, and a wall portionextending between the upper cap and the lower cap when wrapped aroundthe core elements, and the wall portion is perforated.
 19. The methodaccording to claim 13, wherein the structural assembly is cured by atleast one of a room temperature and standard atmospheric pressure cure,and a vacuum autoclave cure.
 20. The method according to claim 13,wherein the structural assembly is formed in a press.